The present invention is directed to a tank system for cold fixing a toner powder on a paper as it is conducted through a fixing station of a non-mechanical high speed printing and/or copying device by exposing the printed paper to an atmosphere enriched with vapors of a fixing agent. The tank system includes a fixing station having an injection tank containing the fixing agent and having means for creating a vapor of the agent in the fixing station, means for collecting a condensate of the vapor of the fixing agent and delivering the condensate to recovery means for separating the fixing agent from the collected condensate and supply means for providing an agent to the injection tank including an exchangeable feed container.
In copiers and non-mechanical high speed printers, the toner powder, which is transferred to a data carrier for example a web of paper, can be fixed with the assistance of vapors of a solvent which is a fixing agent. In this process which is known as a cold fixing process, the endless paper, which is covered with black synthetic powder, is conducted through a chamber in which an atmosphere enriched with the solvent causes the synthetic particles to dissolve and to adhere and thus produces a cross linking adhesion of the powder to the paper. In order to supply the fixing station with the solvent, it has already been proposed that a tank system be used. In this tank system the fixing station itself is preceded by an injection tank through which a liquid fixing agent is sprayed onto a hot plate in the fixing station and is thus vaporized. The injection of the agent from the injection tank is controlled by a sensing device or means which determines the amount or concentration of the vapor in the fixing station and maintains the concentration at a theoretical value. The fixing station itself will also contain a cold sluice in which the consumed fixing agent will be condensed and deposited and is thus mixed with water. The system also has a fixing agent recovery system which contains a water separator which enables recovering of the fixing agent by precipitation from the water. A pump system is used to return the solvent of the fixing agent to the injection tank in the fixing station after appropriate filtering. The recovered agent is then mixed with fresh fixing agent which is supplied from an exchangeable bottle or container.
An essential problem with regard to the transportation of the solvent, which has a decisively low boiling point, occurs when conventional liquid pumps are used. This is due to the low pressure on the suction side of the pump possibly in combination with the increased temperature of the agent resulting in expansion and evaporation which will substantially reduce the conveyance efficiency of the pump and can lead to disturbances resulting from gas formation.
These characteristics of the solvent also necessitate that the entire tank system be hermetically sealed from the environment so as to prevent the undesirable escape of the solvent. Critical zones of such tank systems consist on the one hand in the region of the cold sluice of the fixing station and on the other hand of the coupling zones between the solvent feed containers, which consist of bottles, and the tank system itself.
In order to ensure continuous operation, in particular in non-mechanical high speed printers, it is necessary that the exchangeable feed container should be such as to permit a rapid and problem free exchange or replacement. The supply of solvent to the fixing station should not be interrupted during this exchange process.